On-line analyzers are marketed by the Endress+Hauser Conducta GmbH +Co., KG under the trademark “STAMOLYS”. The analyzers are used in, among other things, the monitoring and optimizing of cleaning performance of a clarification plant, the monitoring of aeration tanks and clarification plant effluent, or the control of filler dosing. Examples of parameters measured and monitored include the concentration of ammonium, phosphate or nitrate in a test sample. The analysis of a test sample occurs on the basis of known measuring methods that do not need to be gone into in greater detail here.
On-line analyzers register daily information preferably continuously as a function of time. They deliver, on the one hand, desired information reliably with respect to the ongoing operation of the plant; on the other hand, information respecting possibly required changes in the process technology are furnished. On the basis of the analysis data, it is possible at times to achieve quite considerable savings in operating means and operating costs.
The working procedure in an on-line analyzer containing a calorimetric measuring device is roughly as follows: a pump fills the permeate—thus, the collected test sample - into a mixing container. A reagents pump feeds to the test sample a suitable reagent in a specified mixing ratio. The reagent reacts with the test sample, whereby the test sample turns color in a characteristic manner. A measurement of the absorption or transmission of radiation directed through the reacted test sample is determined by means of a photometer or a spectrometer. The absorption, or transmission, as the case may be, delivers information on the concentration of a chemical element or a chemical compound in the test sample. Preferably, the temperature of the photometer in the STAMOLYS analyzer is controlled thermostatically, in order that the intended reaction between permeate and reagent can proceed reproducibly and be completed within a short time.
In the case of known analyzers, the photometer with measuring cell, together with the pumps for supply of permeate, reagent and/or cleaning agent, and the valves for switching between internal cycles (calibration, cleaning) , are all accommodated on one mounting frame. Consequently, the electronics for amplifying the optical signals of the optoelectronic components, e.g. the photodiodes, are located in the so-called wet part of the on-line analyzer. In order to protect the sensitive optoelectronic components of the photometer, or spectrometer, as the case may be, against wetness and electromagnetic interference, it is absolutely necessary in the known instances to accommodate the electronics in a separate, sealed, protective housing. In general, the known solution involves relatively many individual components: On the one hand, its assembly is rather complex; on the other hand, the space requirement for the known solution is relatively large.